A process partitioning technique for constructing decentralized web service compositions

Web service compositions have been widely applied in different applications. A service composition is usually implemented in either a centralized or decentralized manner. Compared with the centralized service composition, the decentralized composition has no central control component, and components interact with each other directly, thereby achieving better performance. Process partitioning is a technique to divide a process into multiple parts and has been shown that it can be successfully applied to decentralizing process-driven service compositions. This paper proposes a new process partitioning technique for constructing decentralized service compositions. The proposed technique, which is based on typed digraphs and a graph transformation technique, is used for exploring available process partitioning solutions. For applications, this paper discusses the topology and interaction features about the partitioning solutions and summarizes a ranking method for them. Three experiments are conducted to evaluate the proposed methods in this paper. Experimental results show that the proposed methods can be applied in constructing decentralized service compositions effectively. In addition, the results also show that the decentralized compositions can have lower average response times and higher throughputs than the corresponding centralized compositions in the experiments.     

A graph-theoretic method to find decentralized fixed modes of LTI systems

This paper deals with the decentralized pole assignability of interconnected systems by means of linear time-invariant (LTI) controllers. A simple graph-theoretic approach is proposed to identify the distinct decentralized fixed modes (DFMs) of the system, i.e., the unrepeated modes which cannot be moved by means of a LTI decentralized controller. The state-space representation of the system is transformed to the decoupled form using a proper change of coordinates. For any unrepeated mode, a matrix is then computed which resembles the transfer function matrix of the system at some point in the complex plane. A bipartite graph is constructed accordingly in terms of the computed matrix. Now, the problem of verifying if this mode is a DFM of the system reduces to checking if the constructed graph has a complete bipartite subgraph with a certain property. The sole restriction of this work is that it is only capable of identifying the distinct DFMs of a system. However, it is axiomatic that most of the modes of the real-world systems are normally distinct. The primary advantage of the present paper is its simplicity, compared to the existing ones which often require evaluating the rank of several matrices.     

Enhancing decentralized service discovery in open service-oriented multi-agent systems

Service-oriented multi-agent systems are dynamic systems that are populated by heterogeneous agents. These agents model their functionality as services in order to allow heterogeneous agents or other entities to interact with each other in a standardized way. Furthermore, due to the large-scale and adaptative needs of the system, traditional directory facilitators or middle-agents are not suitable for the management of agent services. This article proposes the introduction of homophily in service-oriented multi-agent systems to create efficient decentralized and self-organized structures where agents have a greater probability of establishing links with similar agents than with dissimilar ones. This similarity is based on two social dimensions: the set of services that an agent provides and the organizational roles that it plays. A second contribution is an algorithm for service discovery that it is carried out taking into account the local information that is related to the homophily between agents. The experiments compare our proposal with other proposals in distributed environments. The results show that the proposed structure and algorithm offer desirable features for service discovery in decentralized environments. Specifically, these features provide short paths and a high success rate in the service discovery process and resilience under deliberate failures.     

A decentralized coordination method for optimal load redistribution in heterogeneous service grids

The optimal load redistribution problem is solved in this paper for heterogeneous non‐dedicated service grids in a decentralized way. A coordination policy is proposed to make networked servers reach their optimal generic task acceptance rates in order to minimize the average service time of all the generic tasks in a grid. Autonomous servers networked in the grid only need to coordinate with their neighbors iteratively, and their optimal generic acceptance rates are reached by task migration among them. The design scheme of the policy is introduced, and the convergence properties and the implementation aspects of the coordination system are discussed in detail in this paper. A set of computer simulations have been conducted, validating the effectiveness of the proposed approach. Copyright © 2010 John Wiley & Sons, Ltd.     

面向Web服务测试的单线执行序列生成方法

测试用例自动生成是实现Web服务自动化测试的关键,基于代数规约的传统测试技术均依赖于创建、初始化和复制被测对象等操作来验证测试结果的正确性,但第三方Web服务并不支持这些操作,无法将测试用例转换成可执行操作序列。一种可行的解决方案是将测试用例转换成只包含一个被测服务实例、不包括实例初始化、只对实例进行状态修改和检查的线性执行序列。改进已有工作,提出包含逆项的测试执行图TEG-I来描述测试用例执行过程中的状态变化,设计TEG-I构造算法和单线执行序列生成算法并实现相应原型工具。实验结果表明,提出的方法能够有效地自动完成测试用例生成,提高Web服务的可测试性。     

Using linguistic features to automatically extract web page title

Existing methods for extracting titles from HTML web page mostly rely on visual and structural features. However, this approach fails in the case of service-based web pages because advertisements are often given more visual emphasize than the main headlines. To improve the current state-of-the-art, we propose a novel method that combines statistical features, linguistic knowledge, and text segmentation. Using annotated English corpus, we learn the morphosyntactic characteristics of known titles and define a part-of-speech tag patterns that help to extract candidate phrases from the web page. To evaluate the proposed method, we compared two datasets Titler and Mopsi and evaluated the extracted features using four classifiers: Naïve Bayes, k-NN, SVM, and clustering. Experimental results show that the proposed method outperform the solution used by Google from 0.58 to 0.85 on Titler corpus and from 0.43 to 0.55 on Mopsi dataset, and offers a readily available solution for the title extraction problem.     

A structural-semantic web service selection approach to improve retrievability of web services

Service-Oriented Computing promotes building applications by consuming and reusing Web Services. However, the selection of adequate Web Services given a client application is still a major challenge. The effort of assessing and adapting candidate services could be overwhelming due to the “impedance” of Web Service interfaces expected by clients versus the actual interfaces of retrieved Web Services. In this work, we present a novel structural-semantic approach to help developers in the retrieval and selection of services from a service registry. The approach is based on a comprehensive structural scheme for service Interface Compatibility analysis, and WordNet as the semantic support to assess identifiers of operations and parameters. We also empirically analyze, compare and contrast the performance of three service selection methods: a pure structural approach, a pure semantic approach, and the structural-semantic (hybrid) approach proposed in this work. The experimental analysis was performed with two data-sets of real-world Web Services and a service discovery support already published in the literature. Results show that our hybrid service selection approach improved effectiveness in terms of retrievability of Web Services compared to the other approaches.     

A simple method to derive minimal cut sets for a non-coherent fault tree

Minimal cut sets (or prime implicants: minimal combinations of basic event conditions leading to system failure) are important information for reliability/safety analysis and design. To obtain minimal cut sets for general non-coherent fault trees, including negative basic events or multi-valued basic events, a special procedure such as the consensus rule must be applied to the results obtained by logical operations for coherent fault trees, which will require more steps and time. This paper proposes a simple method for a non-coherent fault tree, whose top event is represented as an AND combination of monotonic sub-trees. A "monotonic" sub-tree means that it does not have both positive and negative representations for each basic event. It is proven that minimal cut sets can be obtained by a conventional method for coherent fault trees. An illustrative example of a simple event tree analysis shows the detail and characteristics of the proposed method.     

地图符号服务与地图服务的耦合

为了实现地图符号在地图服务(WMS)中的应用,达到灵活定制WMS可视化效果的目的,从支持WMS的图层样式描述规范(SLD)入手,通过对SLD和WMS的分析,研究网络地图符号的发布方法,设计地图符号服务框架,提出了基于SLD,地图符号服务与WMS的耦合方法,以解决基于WMS的WebGIS应用中无法通过符号改变地图可视化效果的问题,实验结果表明该方法可以有效地关联地图符号服务与WMS,实现了WMS可视化效果的灵活定制.     

Graph-theoretic characterization of fixed modes in centralized and decentralized control

A closed-loop system is represented by a weighted directed graph which exhibits all couplings of the system in a very clear and simple manner. The coefficients of the characteristic polynomial of the closed-loop system may be obtained with the aid of cycle families in this graph. Based on this result, a criterion for the existence of fixed modes is derived. The multiplicities of fixed modes may also be determined graph-theoretically. The consequences of structural constraints on the output feedback pattern become evident. Decentralized feedback is discussed as a special case.     

A simple method to derive bounds on the size and to trainmultilayer neural networks

A new derivation is presented for the bounds on the size of a multilayer neural network to exactly implement an arbitrary training set; namely the training set can be implemented with zero error with two layers and with the number of the hidden-layer neurons equal to #1>/= p-1. The derivation does not require the separation of the input space by particular hyperplanes, as in previous derivations. The weights for the hidden layer can be chosen almost arbitrarily, and the weights for the output layer can be found by solving #1+1 linear equations. The method presented exactly solves (M), the multilayer neural network training problem, for any arbitrary training set.     

The practical application of a process for eliciting and designing security in web service systems

Best practices currently state that the security requirements and security architectures of distributed software-intensive systems should be based on security risk assessments, which have been designed from security patterns, are implemented in security standards and are tool-supported throughout their development life-cycle. Web service-based information systems uphold inter-enterprise relations through the Internet, and this technology has been revealed as the reference solution with which to implement Service-Oriented Architectures. In this paper, we present the application of the Process for Web Service Security (PWSSec), developed by the authors, to a real web service-based case study. The manner in which security in inter-organizational information systems can be analyzed, designed and implemented by applying PWSSec, which combines a risk analysis and management, along with a security architecture and a standard-based approach, is also shown. We additionally present a tool built to provide support to the PWSSec process.     

A tools-system in decentralized production management systems

A “Multi-Layered Parallel Production Management” concept and its support tools-system for decentralized production management are proposed, on the basis of a “Sector optimization” concept and a “Tools-system” concept. The necessity for introducing a production system decentralization with a long range/total systematic view, for realizing a flexible and effective production management, is first discussed. Then, discussion is centered on production management quality enhancement and its support methodology. Further, a tools-system for “Multi-Layered Parallel Production Management” support is proposed and its applications are discussed.     

A method to derive texture-relief from ASTER bands 3N and 3B

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard the TERRA satellite generates a pair of bands from which a stereoscopic view can be derived. These bands, called 3N and 3B, correspond to the spectral range 0.78–0.86 μm. In this work, a method based on principal component analysis (PCA) was used to derive, from these bands, the texture-relief of the terrain. We compare our method with a digital elevation model (DEM) obtained from an algorithm that takes advantage of the stereoscopic view. Two examples are presented and discussed in detail.     

A historical and contemporary study on annotations to derive key features for systems design

This paper provides a comprehensive study on annotations by defining their contours and complexity. This work adds a new complementary approach to the usual case and user studies, and also investigates history in order to benefit from previous knowledge and our cultural heritage. This study emphasizes an aspect which has never previously been taken into account: the temporal dimension involved in annotations. Moreover, it discusses both the notion of hypertext between documents and annotations and the idea of annotations as context for documents. The study gives the necessary historical and cultural background to derive a set of key features of annotations that must be taken into account when designing systems that have to support the management of digital annotations on digital contents.     

A similarity method to derive turbulence parameters and mixed-layer depth from sodar measurements

In this paper a summary is given of a similarity method which enables an indirect estimation of mixed-layer depth, surface heat flux and friction velocity from sodar measurements of the mean horizontal wind, and the vertical velocity variance. The results are compared with direct measurements from the Oresund experiment, which was carried out during the period 15 May-14 June 1984.

The similarity method is intended for use in the convective planetary boundary layer     

Fault-tolerant decentralized H-infinity control for multi-channel systems using homotopy method

This paper considers a fault-tolerant decentralized H-infinity control problem for multi-channel linear time-invariant systems. The purpose is to design a decentralized H-infinity output feedback controller to.stabilize the given system and achieve a certain H-infinity performance requirement both in the normal situation and in the situation where any one of the local controllers fails. The designed problem is reduced to a feasibility problem of a set of bilinear matrix inequalities （BMIs）. An algorithm is proposed to solve the BMIs. First, the normal situation is considered where all the local controllers are functioning. The local controllers are obtained from a standard centralized H-infinity controller by using a homotopy method imposing a structural constraint progressively. Secondly, the above case is extended to the one where any one of the local controllers fails. We again use a homotopy method where the coefficient matrices of the failed controller are decreased progressively to zero. The efficiency of the proposed algorithm is demonstrated by an example.     

Web服务与目录服务在系统集成中的应用研究

随着企业网上运行的应用服务不断增多,如何把各种不同的服务系统集成起来成为网络应用服务领域所面临的重大问题.目录服务与Web服务的结合为不同应用系统的集成提供了新的解决方案.目录服务能够实现对用户信息和网络资源的统一管理,Web服务能够将众多异构应用系统有机的结合起来,而基于目录的UDDI Web服务注册中心则又实现了目录对Web服务的统一管理.给出了一个利用目录和Web服务解决校园网络应用系统集成的方案.     

Fault-tolerant decentralized H-infinity control for multi-channel systems using homotopy method

This paper considers a fault-tolerant decentralized H-infinity control problem for multi-channel linear time-invariant systems. The purpose is to design a decentralized H-infinity output feedback controller to stabilize the given system and achieve a certain H-infinity performance requirement both in the normal situation and in the situation where any one of the local controllers fails. The designed problem is reduced to a feasibility problem of a set of bilinear matrix inequalities (BMIs). An algorithm is proposed to solve the BMIs. First, the normal situation is considered where all the local controllers are functioning. The local controllers are obtained from a standard centralized H-infinity controller by using a homotopy method imposing a structural constraint progressively. Secondly, the above case is extended to the one where any one of the local controllers fails. We again use a homotopy method where the coefficient matrices of the failed controller are decreased rogressively to zero. The efficiency of the proposed algorithm is demonstrated by an example.